Recurrent species groups were formed by computer analysis from the data on occurrence of demersal fish at 480 trawl stations in the tropical eastern Atlantic; these recurrent groups were then marshalled into a small number of major species assemblages, or communities in the wide sense, on the basis of intergroup relationships. These assemblages proved to be remarkably similar in composition and ecology to the communities of demersal fish recognized earlier by a number of authors from their subjective analysis of trawling survey data in this region. The computer analysis provided finer detail on both the structure and distribution of the assemblages and their constituent groups. This confirmation of the reality of the subjectively recognized communities suggests (1) that the recognition of such assemblages by subjective methods has a place in the assessment of multispecies fish resources but (2) that where the method is practicable, the machine processing of recurrent species groups in the analysis of trawl survey data can be a valuable tool in resource evaluation.